Thermoplastic materials and article made therefrom

ABSTRACT

The present invention provides a thermoplastic composition excellent in heat resistance and water resistance which includes a thermoplastic saturated norbornene polymer which has a number-average molecular weight (Mn) of 50,000-500,000 and a weight-average molecular weight (Mw) of 100,000-2,000,000 which are measured by high performance liquid chromatography, and a molecular weight distribution (Mw/Mn) of 2.2 or more, and a volatile content of at most 0.3% by weight higher. The composition is suitable for optical materials, electroconductive composite materials and optical recording media.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thermoplastic material excellent inheat resistance and water resistance which comprises thermoplasticsaturated norbornene polymer and more particularly, to a thermoplasticmaterial which can provide articles excellent in strength and free fromdefects caused by blowing especially when it is extrusion formed.

The present invention further relates to a film-like or sheet-likearticle made from the above thermoplastic material and excellent instrength and free from fine defects.

Moreover, the present invention relates to an optical material made fromthe above thermoplastic material and excellent in transparency and anelectroconductive composite material and an optical recording mediummade from the above material.

2. Related Art

In general, polyolefinic polymers have such structure as consisting ofonly carbon and hydrogen and having no unsaturated bond and therefore,have the features that they are low in affinity with water and do notabsorb or permeate water and besides, are high in resistance to acid,alkali and other chemicals or various solvents.

Representatives thereof are polyethylene and polypropylene and these areemployed for various uses in the form of sheet, film, pipe, rod, and thelike formed by melt extrusion. However, these conventional materialssuffer from the problems that they are insufficient in heat resistanceand become distorted at relatively low temperatures of 70°-80° C. orlower and cannot be used at a temperature higher than such temperature.Furthermore, these materials are low in transparency and cannot be usedfor optical purposes.

On the other hand, polycarbonate (PC) and polymethyl methacrylate (PMMA)have been mainly used as optical transparent plastic materials foroptical disc substrate, plastic lens and the like. However, PC is highin birefringence and PMMA is high in water absorption and insufficientin heat resistance. Thus, these materials are not enough to meet theincreasingly heightened demands.

Recently, attention has been given to thermoplastic saturated norbornenepolymers such as hydrogenated products of ring opening polymers ofnorbornene monomers and addition polymers of norbornene monomers andethylene as optical plastic materials such as optical disc substrate.(Japanese Patent Kokai Nos. Sho 60-26024 and 63-31752 and Hei 1-24826,EP 303246 and EP 317262, and U.S. Pat. No. 4614778).

These thermoplastic saturated norbornene polymers are a kind ofpolyolefin polymers and have excellent water resistance, chemicalresistance and solvent resistance like other polyolefin polymers andbesides, polymers having a high heat resistance of higher than the glasstransition temperature 100° C can be synthesized. Furthermore, they havea total light transmittance of 90% or higher and thus, are superior intransparency.

Therefore, thermoplastic saturated norbornene polymers not only have thepossibility of being used for various uses as polyolefin materialshaving heat resistance, but also have the possibility of being developedfor optical uses as transparent materials having both the lowbirefringence and excellent transparency, water resistance and heatresistance.

However, these thermoplastic saturated norbornene polymers are brittleas compared with polyethylene, polypropylene and PMMA and, whenextrusion formed into sheet, film, and rod, are apt to crack or breakand articles of sufficient strength have not been obtained. There arefurther problems that a bubble-like defect is often generated inextrusion formed articles, which appears on the surface in the form ofvisible streaks or which reduces strength. Even if visible large streaksare not present, in many cases, observation in detail under lightmicroscope reveals invisible fine voids or crack-like defects(hereinafter referred to as "microvoid") generated inside of the moldedarticles. Thus, hitherto, extrusion formed articles of thermoplasticsaturated norbornene polymers with no microvoids have not been obtained.

As other method for obtaining sheet-like or film-like articles, there isa casting method which comprises casting a polymer as a solution in asuitable solvent and evaporating the solvent and according to thismethod there are obtained articles having substantially no microvoids.However, even if it is a thin article of a few μm in thickness, solventcannot be completely evaporated and a few % of solvent remains andsufficient strength cannot be obtained. Furthermore, the remainingsolvent gradually evaporates during using the article to changeproperties of the article or the evaporated solvent adversely influencesother parts provided around the article. From the point of endurance,film-like or sheet-like articles are required to have a tensile strengthof at least 800 kg/cm², preferably at least 900 kg/cm², but those whichhave such sufficient strength have not been obtained by casting method.

Therefore, hitherto, there have not yet been provided sheet-like orfilm-like articles comprising a thermoplastic saturated norbornenepolymer which have no defects such as microvoids and cracks and havesufficient strength of at least 800 kg/cm² in tensile strength.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a thermoplasticmaterial excellent in heat resistance and water resistance.

One aspect of the present invention is directed to a material comprisingthermoplastic saturated norbornene polymers which provides articlessuperior in strength and free from defects due to blowing or streakingand microvoids especially when it is extrusion formed and an articlecomprising the above material.

Another aspect of the present invention is directed to an opticalmaterial excellent in transparency which comprises the above material,and an electroconductive composite material and an optical recordingmedium made from the above material.

As a result of intensive research conducted by the inventors in anattempt to solve the above-mentioned problems, it has been found thatthermoplastic saturated norbornene polymers having a proper range ofmolecular weight and a proper range of molecular weight distributionhave sufficient strength when molded or formed.

Conventional thermoplastic saturated norbornene polymers containunreacted monomers and low voltatile components such as solvent and ithas been found that these cause reduction of strength or formation ofstreaks on the surface due to blowing. Accordingly, when content of thelow volatile component in the polymers is reduced to 0.3% by weight orless, blowing and formation of large visible streaks can be inhibitedeven when the polymers are extrusion formed. Moreover, it has beenrecognized that some antioxidants added to thermoplastic saturatednorbornene polymers promote the reduction of strength and formation ofsurface streaks caused by blowing, but it has been found that when aspecific low volatile antioxidant is selected and used, the problemssuch as decomposition, deterioration and coloration of polymers can besolved without damaging the characteristics of the polymers.

Furthermore, even if extrusion formed articles of thermoplasticsaturated norbornene polymers appear to have no defects by visualexamination, there are often present microvoids or crack-like defects ininner part of the article when observed in detail by light microscopeand the like. As a result of intensive research in order to solve theseproblems, it has been found that when pellets obtained by melt extrusionare dried under high temperature conditions, for example, hightemperature of somewhat lower than glass transition temperature (Tg)before subjected to extrusion molding and then are used, molded orformed products free from microvoids can be obtained. This dryingtreatment is effective also when the material is injection molded andthe thus obtained molded articles are also excellent in endurance underhigh temperature and high humidity and microvoids are not formed for along period of time.

As explained above, the inventors have found that thermoplastic materialwhich can provide transparent articles having no defects in inner partand on the surface can be obtained by controlling molecular weight andmolecular weight distribution of thermoplastic saturated norbornenepolymers to specific ranges and reducing content of volatile componentto less than a specific amount and by selecting and using a low volatileantioxidant.

This thermoplastic material shows no irregular reflection of light, isexcellent in optical characteristics and provides articles excellentalso in strength, water resistance and heat resistance, and so isespecially suitable as optical material. Furthermore, since the moldingmaterial is high in heat resistance and does not permeate water,electroconductive composite material of high endurance can be obtainedby forming an electroconductive layer on an article made from thematerial. Further, it has been found that an optical recording mediumexcellent in various characteristics can be obtained by providing arecording thin film which can perform optical recording and/or readingon a transparent substrate made from the above material.

The present invention has been accomplished based on these findings.

Thus, the present invention provides a molding or forming materialcomprising a thermoplastic saturated norbornene polymer, characterizedin that it has a number-average molecular weight (Mn) of 50,000-500,000and a weight-average molecular weight (Mw) of 100,000- 2,000,000measured by hi9h performance liquid chromatography and a molecularweight distribution (Mw/Mn) of 2.2 or more, and amount of volatilecomponent contained in the polymer is 0.3% by weight or less.

Furthermore, the present invention provides a molding or formingmaterial which comprises 100 parts by weight of the above-mentionedthermoplastic saturated norbornene polymer and 0.01-5 parts by weight ofan antioxidant having a vapor pressure of 10⁻⁶ Pa or less at 20° C.

Moreover, the present invention provides the above-mentioned materialwhich has been pelletized by melt extrusion and then dried at hightemperature.

In addition, the present invention provides a film-like or sheet-likearticle formed of the above material, an optical material, anelectroconductive composite on which an electroconductive film isformed, and a optical recording medium comprising a transparentsubstrate comprising the above film-like or sheet-like article on whichis provided a recording thin film capable of performing opticalrecording and/or reading.

DETAILED DESCRIPTION OF THE INVENTION

(Thermoplastic saturated norbornene polymer)

The molding or forming material aimed at by the present invention is athermoplastic saturated norbornene polymer and examples thereof arepolymers having structural units represented by the following formulas[I] and/or [II]. ##STR1## [wherein R₁ and R₂ each represents a hydrogenatom, a hydrocarbon residue or a polar group such as halogen, ester,nitrile, pyridyl, or the like and may be identical or different andbesides, R₁ and R₂ may form a ring together, n represents a positiveinteger and q represents 0 or a positive integer]. ##STR2## [wherein R₃and R₄ each represents a hydrogen atom, a hydrocarbon residue or a polargroup such as halogen, ester, nitrile, pyridyl or the like and may beidentical or different and R₃ and R₄ may form a ring together, ( and meach represents a positive integer and p represents 0 or a positiveinteger].

The polymer having the structural unit represented by the formula [I]isa saturated polymer prepared by hydrogenation, by usual hydrogenationprocess, of a ring opening polymer obtained by polymerization of one ormore of the following monomers by known ring opening polymerization:norbornene; its alkyl and/or alkylidene substituted compounds such as5-methyl-2-norbornene, 5,6-dimethyl-2-norbornene, 5-ethyl-2-norbornene,5-butyl-2-norbornene, and 5-ethylidene-2-norbornene; dicyclopentadieneand 2,3-dihydrodicyclopentadiene and these compounds substituted withalkyl such as methyl, ethyl, propyl or butyl or polar group such ashalogen; dimethanooctahydronaphthalene and this compound substitutedwith alkyl, alkylidene or polar group such as halogen such as6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-ethylidene-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-chloro-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-pyridyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, and6-methoxycarbonyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene; and trimers-tetramers ofcyclopentadiene such as4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene and4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene.

In order to obtain the objective hydrogenated ring opening polymers(saturated polymer) having a glass transition temperature (Tg) of 100° Cor higher, it is preferred to use tetracyclic or pentacyclic monomersamong these norbornene monomers or to use these tetracyclic orpentacyclic monomers as main component in combination with dicyclic ortricyclic monomers. From the point of birefringence, it is especiallypreferred to use tetracyclic lower alkyl substituted monomer oralkylidene substituted monomer as main component. The lower alkyl oralkylidene group is preferably of 2-3 carbon atoms.

The polymer having the structural unit represented by the formula [II]is a polymer obtained by addition copolymerization of at least one ofthe above-mentioned norbornene monomers and ethylene as monomers byknown process and/or a hydrogenated product of the resulting polymer andthese are all saturated polymers.

Furthermore, the thermoplastic saturated norbornene polymers may bepolymers obtained by preparing polymer [I] or [II] in the presence ofα-olefins such as 1-butene, 1-pentene and 1-hexene as molecular weightmodifier or by copolymerization of the above monomers with other monomercomponents, e.g., cycloolefins such as cyclopropene, cyclobutene,cyclopentene, cycloheptene, cyclooctene, and 5,6-dihydrocyclopentadieneadded as a minor component.

The thermoplastic saturated norbornene polymers in the present inventionmust have a number-average molecular weight (Mn) of 50,000-500,000,preferably 60,000-200,000 and a weight-average molecular weight (Mw) of100,000-2,000,000, preferably 100,000-1,000,000 which are measured byhigh performance liquid chromatography (HLC) analysis using toluene assolvent and a molecular weight distribution (Mw/Mn) of 2.2or more.

If Mn and Mw are less than the above ranges, extrusion formed articlessuch as film, sheet and rod do not have sufficient strength. To thecontrary, if Mn and Mw are larger than the above ranges, moldability isinferior and extrusion forming is difficult because of too highviscosity. Besides, when the polymer is dissolved in a suitable solventfor casting or spinning, solubility in solvent is insufficient. Besides,synthesis reaction for polymer of such high molecular weight isdifficult to control and there is the disadvantage that material ofstable quality cannot be obtained.

Moreover, molecular weight distribution (Mw/Mn) must be 2.2 or more andpreferred is 2.4 or more and especially preferred is 2.8 or more.

It is generally considered that thermoplastic polymers smaller inmolecular weight distribution and close to monodispersion ar superior inbalancing between strength and moldability and superior in performance.However, when such polymer as of the present invention which hasrelatively high molecular weight is extrusion formed, for example, intoa sheet or a film, stress is not retained and flat and beautifularticles as a whole can be obtained in the case where molecules ofvarious molecular weights gradually solidify in the order of from themolecule higher in molecular weight to the molecule lower in molecularweight as compared with the case where monodispersed moleculesinstantaneously and simultaneously solidify at a certain temperature inthe course of solidification of polymer from molten state with cooling.This tendency is especially conspicuous for thermoplastic saturatednorbornene polymer because the polymer is rigid and high in heatresistance and molding or forming temperature reaches considerably hightemperature near 300° C. Therefore, for attaining the object of thepresent invention, molecular weight distribution must be 2.2 or more andis preferably 2.4 or more and especially preferably 2.8 or more. If themolecular weight distribution is lower than the above range, there arethe defects that extrusion forming is difficult and formed articlessuperior in smoothness and optical characteristics are obtained withdifficulty.

With increase in molecular weight distribution (Mw/Mn), moldability isimproved. In general, in polymers such as polycarbonate which are highin heat resistance and rigidity, the phenomenon is apt to occur thatwhen they are rapidly cooled from molten state, strain is generatedinside the polymers and flat articles cannot be obtained. The samephenomenon may also occur in thermoplastic norbornene polymers. Forexample, when the polymer is extruded from T-die of extruder and takenoff in the form of a sheet, a flat sheet cannot be drawn unless rolltemperature is raised. In the case of polymer having a Tg of about 140°C., it can be drawn in the form of flat sheet by raising rolltemperature to 120°-140° C. However, in many cases, heating of roll iscarried out with water and so the roll temperature can only be raised toat most about 90° C.

If molecular weight distribution is less than 2.2, molding or formingcannot be satisfactorily performed even when roll temperature is raisedto about 140° C which is close to the glass transition temperature ofthe polymer while when the molecular weight distribution is 2.2 or more,a flat article can be obtained by raising roll temperature to about110°-130° C. Furthermore, when the molecular wight distribution isextended to 2.8 or more, moldability is further improved and a flatarticle free from internal strain can be obtained even at a rolltemperature of about 90°-100° C.

There is no special upper limit in molecular weight distribution, but ifit is too large, Mn is large and sufficient strength cannot be obtainedin spite of the high melt viscosity and besides, synthesis of suchpolymer per se becomes difficult. Therefore, in general, it ispreferably about 6.0 or less.

Thermoplastic saturated norbornene polymers having such molecularweights (Mn, Mw) and molecular weight distribution (Mw/Mn) can beproduced, for example, in the following manner: In synthesis reaction,amount of catalyst used is changed or polymerization temperature ischanged; in the case of using a molecular weight modifier, kind oramount thereof is changed; monomers are added later to the reactionsystem by prop; or polymer of low molecular weight and that of highmolecular weight are separately prepared and these are blended to extendthe molecular weight distribution.

When unsaturated bond remaining in molecular chain of the synthesizedpolymer is saturated by hydrogenation reaction, hydrogenation rate is90% or more, preferably 95% or more, especially preferably 99% or morefrom the points of photo-deterioration resistance and weatheringresistance.

From the points of heat resistance and moldability, the polymer in thepresent invention preferably has a Tg of 100° C. or higher, preferably120°-200° C., more preferably 130°-180° C.

(Method for reducing volatile content)

Thermoplastic saturated norbornene polymers obtained by usual synthesismethod generally contain 0.5% by weight or more of volatile component.

In the molding or forming material of the present invention, content ofvolatile component in thermoplastic saturated norbornene polymer is 0.3%by weight or less, preferably 0.2% by weight or less and more preferably0.1% by weight or less.

In the present invention, loss in weight on heating of from 30° C. to350° C. is obtained by a differential thermal weight measuring apparatus(TG/DTA200) manufactured by Seiko Electronics Industries, Ltd. and thisis taken as content of volatile component.

If the content of volatile component is more than the above range, whenthe polymer is extrusion formed at a temperature of about 250°-350° C.,the volatile component is volatilized during forming to cause blowing,resulting in defects in the article or reduction of strength or streakson the surface of the article.

For reducing content of volatile component, for example, there ispolymer coagulation method using a bad solvent where coagulation isrepeatedly by carried out. In the case of direct drying method, it isdesired to carry out drying at higher than 250° C. and under less than30 Torr using a thin film dryer or extrusion dryer. It is also possibleto carry out direct drying after solvent solution of polymer isconcentrated to several ten %. Of course there is no limitation inmethod for reduction of volatile content.

Thermoplastic saturated norbornene polymers produced by these methodsare substantially amorphous, are excellent in transparency, dimensionalstability, heat resistance and water absorption, and has substantiallyno moisture permeability.

(Antioxidant)

In the present invention, when 0.01-5 parts by weight of a low volatileantioxidant is added to 100 parts by weight of the thermoplasticsaturated norbornene polymer, decomposition or coloration of the polymerduring molding or forming can be effectively inhibited.

The antioxidant preferably has a vapor pressure of 10⁻⁶ Pa or less at20° C., especially preferably 10⁻⁸ Pa or less. If vapor pressure ishigher than 10⁻⁶ Pa, there are problems that blowing occurs at extrusionforming and the antioxidant volatilizes from the surface of article whenexposed to high temperature.

Antioxidants usable in the present invention include, for example, thefollowing. These can be used singly or in combination of two or more.

Hindered phenol type:

2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butylphenol,4-hydroxymethyl-2,6-di-t-butylphenol,2,6-di-t-butyl-α-methoxy-p-dimethyl-phenol, 2,4-di-t-amylphenol,t-butyl-m-cresol, 4-t-butylphenol, styrenated phenol,3-t-butyl-4-hydroxyanisole, 2,4-dimethyl-6-t-butylphenol,octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenol)-propionate,3,5-di-t-butyl-4-hydroxybenzylphosphonatediethyl ester, 4,4'-bisphenol,4,4'-bis-(2,6-di-t-butylphenol),2,2'-methylene-bis-(4-methyl-6-t-butylphenol),2,2'-methylene-bis-(4-ethyl-6-butylphenol),2,2'-methylene-bis-(4-methyl-6-α-methylcyclohexylphenol),4,4'-methylene-bis-(2-methyl-6-t-butylphenol),4,4'-methylene-bis-(2,6-di-t-butylphenol),1,1'-methylene-bis-(2,6-di-t-butylnaphthol),4,4'-butylidene-bis-(2,6-di-t-butyl-meta-cresol),2,2'-thio-bis-(4-methyl-6-t-butylphenol), di-o-cresol sulfide,2,2'-thio-bis-(2-methyl-6-t-butylphenol),4,4'-thio-bis-(3-methyl-6-t-butylphenol),4,4'-thio-bis-(2,3-di-sec-amylphenol), 1,1'-thio-bis-(2-naphthol),3,5-di-t-butyl-4-hydroxybenzyl ether,1,6-hexanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine,2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],2,2-thio-bis(4-methyl-6-t-buytlphenol),N,N'-hexamethylenebis(3,5-di-ti-butyl-4-hydroxy-hydrocinnamide),bis(3,5-di-t-butyl-4-hydroxybenzylphosphonic acid ethyl ester)calcium,1,3,5-trimethyl-2,4,6-tris-(3,5-di-t-butyl-4-hydroxybenzyl)-benzene,triethyleneglycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate],1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl- 4-hydroxybenzyl)benzene,tris-(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate, andpentaerythrityltetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]etc.,

Aminophenol type:

n-butyl-p-aminophenol, n-butyroyl-p-aminophenol,n-pelargonoylp-aminophenol, n-lauroyl-p-aminophenol,n-stearoyl-p-aminophenol, 2,6-di-t-butyl-α-dimethyl, and amino-p-cresol,etc.

Hydroquinone type:

Hydroquinone, 2,5-di-t-butylhydroquinone, 2,5-di-t-amylhydroquinone,hydroquinone methyl ether, and hydroquinone monobenzyl ether, etc.

Phosphite type:

Triphosphite, tris(2,4-di-t-butylphenyl) phosphite, tris(nonylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene phosphonite,and 2-ethylhexyloctylphosphite, etc.

Others:

2-Mercaptobenzothiazole zinc salt, dicatecholborate-di-o-tolylguanidinesalt, nickel-dimethyldithiocarbamate,nickel-pentamethylenedithiocarbamate, mercaptobenzimidazole, and2-mercaptobenzimidazole zinc salt, etc.

(Other components)

The thermoplastic saturated norbornene polymers of the present inventionmay contain various antistatic agents, lubricants, surface activeagents, ultraviolet absorbers, and the like as far as attainment of theobject of the present invention is not damaged, as additives in additionto the antioxidants. Furthermore, when the polymer is used for usesother than optical materials, if necessary, additives such as fillers,e.g , glass fiber, dyes, and pigments may be added to the polymer.

(Pelletization and predrying)

Plastic material are normally supplied in the form of pellets of about1-7 mm in diameter and about 4-8 mm in length and the pellets weremolded or formed into desired shapes by extrusion forming or injectionmolding. In general, from the polymer synthesized, the solvent used insynthesis is removed by coagulation method or direct drying method andto the polymer were added the above various additives in the necessaryamounts and then, in the case of thermoplastic saturated norbornenepolymer, this is extruded into strands of a given diameter from themolten state at a temperature of about 230° C. or higher and thereafter,the strands are cut to a desired length to make pellets.

In the case of normal plastic materials, the pellets are molded orformed as they are, but in the case of highly hydroscopic or readilydecomposable resins such as polycarbonate resin, acrylic resin, andpolyamide resin, when they are molded or formed as they are, vigorousblowing occurs or defects such as large streaks on the surface ofarticle occur due to water adsorbed to pellets during storage thereofand due to decomposition products, and so it is customary to carry outpredrying at a temperature below glass transition temperature of theresin for several hours before use.

However, thermoplastic saturated norbornene polymers are low inhydroscopicity and do not contain components which decompose duringstorage and hitherto, the predrying has been considered to be needlessand molding or forming has been performed without the predrying.Actually, even if predrying is attempted, substantially no volatilecomponent is detected. However, surprisingly, it has been found thatwhen pellets of thermoplastic saturated norbornene polymers arepredried, articles free from microvoids are obtained while whenpredrying is not conducted, the microvoids, namely, invisible fine voidsor cracks are generated in the articles.

The thus obtained article does not generate microvoids even after moldedor formed and besides, does not generate microvoids even after beingsubjected to endurance test under high temperature and high humidity,for example, higher than 70° C. and higher than 80% in relativehumidity. Furthermore, it has been confirmed that this drying treatmentis effective also in the case of injection molding.

As conditions of the predrying, higher temperature and longer dryingtime are more effective, but if temperature is too high exceeding glasstransition temperature of resin, pellets per se heat fusion-bond to eachother and are difficult to use and the effect saturates in severalhours. Therefore, the predrying is carried out for preferably 1 hour orlonger, more preferably 2 hours or longer at preferably (Tg-30)˜(Tg-5)°C., more preferably (Tg-20) ˜(Tg-5)° C.

Either vacuum drying or atmospheric drying in the air or nitrogenatmosphere is effective for the drying. The period from completion ofdrying treatment to use for molding or forming is preferably as short aspossible, but it is not needed to be especially short and the effect isnot lost even after lapse of several days.

(Molding or forming method)

The thermoplastic saturated norbornene polymer of the present inventionis suitable especially for extrusion forming, but is not limited tothis.

The polymer is heated to about 250°-300° C. and extruded from T-die ormanifold die using a melt extruder and can be forming into sheet or filmby winding-up by various rolls.

In this case, since thermoplastic saturated norbornene polymer is highin heat resistance and in rigidity, if it is rapidly cooled by roll, itcannot be faltly with generating surface waviness as in the case ofpolycarbonate and it is suitable to keep wind-up cooling rolls of thefirst and the second steps at a relatively high temperature of about70°-140° C. according to the value of molecular weight distribution(Mw/Mn) as mentioned before and to carry out gradual cooling. It is alsopossible to further subject the sheet-like article to monoaxial orbiaxial stretching.

In addition, it is also possible to carry out processing by calenderrolling or to carry out coextrusion processing or laminate processingwith other olefin resins such as polyethylene and polypropylene,polyester resins such as polyethylene tetraphthalate or halogenatedhydrocarbon resins such as polyvinyl chloride and polyvinylidenechloride for further improvement of strength and gas permeability.

Moreover, the polymer can be extrusion formed into rod-, fiber- ortube-like article by extruding it from suitable die. These extrusionformed articles can further be processed into the rods or tubes bystretching them at a temperature lower than glass transitiontemperature.

In order to further increase strength, cross-linking can also beeffected by heating or irradiation with a radiations such as ultravioletray and electron beam. In this case, it is effective to use suitablecrosslinking agents. Known crosslinking agents can be used and examplesthereof are monomers having a plurality of vinyl groups such asdivinylbenzene; polyfunctional acrylates such as diallyl phthalate,ethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate;isocyanurates such as triallyl isocyanurate; and polymers having aplurality of unsaturated bonds such as liquid polybutadiene.

The thermoplastic saturated norbornene polymer of the present inventioncan also be molded or formed by the following methods in addition to themelt extrusion forming.

The polymer can be formed into a sheet by hot pressing. Furthermore, thethermoplastic saturated norbornene polymer can be formed into a film bydissolving it in an aromatic hydrocarbon solvent such as benzene,toluene or xylene, an alicyclic hydrocarbon solvent such as cyclohexane,methylcyclohexane or decalin or a halogen based solvent such aschloroform or monochlorobenzene and casting the solution on a flat plateor on a roll. For polymer of relatively high molecular weight, thesolvent solution thereof can be spun into fiber-like article.

Polymer of relatively low molecular weight can be molded to a sheet-likearticle having a thickness of 0.2 mm or more by normal injection moldingand besides, processing method of general thermoplastic resins such asrotational molding can be applied.

(Optical materials and electroconductive composite materials)

The thermoplastic material of the present invention has thecharacteristics that it is amorphous, excellent in transparency andsmall in birefrigerance and so is suitable as various optical materials,especially as substrate materials for optical recording medium.

On the surface of an article made from the material of the presentinvention there may be formed a film of a metal, a metal oxide, a metalnitride, a metal sulfide, a metal halide, or the like by thin filmforming methods such as vacuum evaporation and sputtering in the form ofsingle layer or multi-layer depending on the object. In this case, thearticle is sometimes exposed to a considerably high temperature invacuum, but in the case of the article obtained according to the presentinvention, chamber can be drawn to a given degree of vacuum in a shorttime and furthermore a smooth film free from blister on the surface canbe formed because of low content of volatile component and littleoutgassing.

Further, a recording medium can be produced by providing on atransparent substrate a recording thin film capable of performingoptical recording and/or reading.

Recording materials for forming the recording thin film (recordinglayer) may be known optional rare earth element-transition metalamorphous alloys and as examples thereof, mention may be made of Tb-Fealloys (Japanese Patent Kokoku No. Sho 57-20691), Dy-Fe alloys (JapanesePatent Kokoku No. Sho 57-20692), Cd-Tb-Fe alloys (Japanese Patent KokaiNo. Sho 56-126907), Cd-Tb-Dy-Fe alloys (Japanese Patent Kokai No. Sho57-94948), Cd-Co alloys (Japanese Patent Kokai No. Sho 54-121719), andTb-Fe-Co alloys. This rare earth element-transition metal amorphouslayer is preferably formed by thin film forming methods such as vacuumevaporation, sputtering and ion plating. Thickness of this amorphouslayer is generally 500-1500 Å.

Furthermore, a phase change type recording material may be used asrecording layer. Examples thereof are those of Ge-Te type, Sb-Te type,In-Sb type, Ge-Sb-Te type, and In-Sb-Te type. These phase change typerecording materials are preferably formed into a recording layer byvacuum evaporation, sputtering, ion plating or the like. Thickness ofthis amorphous layer is generally 500-2000 Å.

Organic dye recording materials may also be used and as examples of suchmaterials, mention may be made of methine.polymethine type(cyanine:indolonine type, thiazole type) (Japanese Patent Kokai No. Sho58-1713696); quinones such as naphthoquinones and anthraquinones(Japanese Patent Kokai Nos. Sho 59-199291 and 58-112793); phthalocyaninetype (metallo-phthalocyanines) (Japanese Patent Kokai Nos. Sho 612235188and 59-11292); dithiol type (dithiol metal complexes) (Japanese PatentKokai No. Sho 57-11090); and other tetrahydrochlorines, dioxanes,dithiazines, thiapyryliums and porphyrins (Japanese Patent Kokai Nos.Sho 58-197088, 61-235188 and 59-78891). Thickness of film formed fromthese organic dye recording materials is generally 500-5000 Å.

Moreover, the molding material of the present invention can be utilizedfor erasable type recording card with using, for example, Te-CS₂,Pb-Te-Se, Te-C, TeO₂, Sb-Se, or Bi-Te, or using change of shape such asbubble formation.

In addition, gold, platinum, aluminum and the like may be used as areflective film.

In the optical recording medium, there may be provided a surfaceprotective layer on the surface or a protective layer, reflective layeror a dielectric layer between the recording layer and the substratecomprising the polymer of the present invention. Materials for theseprotective layer and others include, for example, inorganic materialssuch as CdS, ZnSe, SiO₂, Si, Si₃ N, Si₃ N₄, AlN, TiO₂, TaO₂, and MgF₂and organic materials such as ultraviolet-curing resins.

For optical card, there may be laminated directly with other materialsand in this case, lamination can be carried out using general adhesivessuch as solvent type hot melt type and UV curing type adhesives andbesides, high frequency and ultrasonic adhesion methods may also beemployed.

(Uses)

The material of the present invention is effective for uses such asplastic optical fibers for short-distance information transmissionincluding for automobiles and medical purpose and connector for theoptical fibers; plastic lenses such as lens for pick-up of information,lens for projectors, spectacle lens, goggles for sports, and lens forhead lamp and tail lamp of automobiles and others; transparent platesfor information display such as touch electrode or liquid crystalsubstrate provided with a transparent electroconductive film andantidazzling filters for screen, polar film and CRT; insulating film andmoistureproof coating for electronic devices with utilizing itsmoistureproof and insulating properties; medical instruments such asinjector, pipette, container for medicines, and vessel or film foroptical analysis; window materials such as front glass of automobiles,windshield of motorbikes, window material of aircrafts, housing window,transparent shutter, and lighting fixture, and mirrors; beveragecontainers for juice, alcoholic drink and carbonated beverages and foodcontainers; packaging films; and moistureproofing paints prepared bydissolving in solvent with addition of suitable filler, dye, pigment orthe like.

For uses as composite materials made by forming an electroconductivefilm on the surface, there are uses for touch electrode and liquidcrystal substrate with providing a transparent film and electronicdevices such as high-frequency circuit substrate and film forcapacitors.

For optical recording materials provided with recording thin film on thesurface, the material of the present invention is effective asreflective type and dye type information recording media, for example,various memories for computers such as optical card, optical floppy,optical type and others.

The present invention will be explained by the following nonlimitingexamples and comparative examples, wherein part and % are by weightunless otherwise notified.

EXAMPLE 1

(preparation of ring opening polymer)

In a 200 liter reaction vessel were changed 90 parts of dehydratedtoluene, 0.5 part of triethylaluminum, 1.4 part of triethylamine, and0.08 part of 1-hexene under nitrogen atmosphere.

While keeping the temperature at 20° C., 30 parts ofethyltetracyclododecene (ETD) and 0.17 part of titanium tetrachloridewere continuously added to the reaction system over a period of 1 hourto carry out polymerization reaction. The reaction was allowed toproceed for 1 hour after addition of total amount of EDT and titaniumtetrach oride.

Thereafter, isopropyl alcohol/aqueous ammonia (0.5 part/0.5 part) mixedsolution was added to stop the reaction and the reaction product waspoured into 500 parts of isopropyl alcohol to coagulate it. Thecoagulated polymer was vacuum dried at 60° C. for 10 hours to obtain25.5 parts of a ring opening polymer as a dry polymer.

(Hydrogenation reaction)

The resulting ring opening polymer was dissolved in 200 parts ofcyclohexane and hydrogenation reaction was carried out in a 200 literautoclave with addition of 0.6 part of palladium/carbon catalyst(supporting amount: 5%) at 140° C. under a hydrogen pressure of 70kg/cm² for 4 hours.

(After-treatment)

The hydrogenation catalyst was removed by filtration and then reactionmixture was poured into 600 parts of isopropyl alcohol to carry outcoagulation.

The resulting hydrogenated product was vacuum dried at 60° C. for 10hours and then redissolved in cyclohexane to prepare a 10% solution.This solution was poured into 600 parts of isopropyl alcohol to againcoagulate it. In the same manner as above, drying, coagulation werecarried out once more and the hydrogenated product obtained was vacuumdried at 90° C. for 48 hours to obtain 22.6 parts of a hydrogenatedproduct. Yield was 75%.

(Characteristics of polymer)

Hydrogenation rate of the resulting hydrogenation product was 99% orhigher according to 1H-NMR spectrum analysis. Molecular weight (in termsof polystyrene) of the product was measured by high performance liquidchromatography (HLC) analysis using toluene as a solvent (by HLC 802Lmanufactured by Toso Co. with TSK gel G5000H-G4000H as column at flowrate of 1.0 ml/min at 38° C.) to obtain a number-average molecularweight (Mn) of 7.0×10⁴ and a weight-average molecular weight (Mw) of17.5×10⁴ and molecular weight distribution (Mw/Mn) was 2.5.

Glass transition temperature (Tg) was measured by DSC analysis andcontent of volatile component was measured by thermogravimetric analysis(TGA) as loss in weight on heating from 30° C. to 350° C. at heatingrate of 10° C./min in nitrogen atmosphere to obtain Tg of 142° C. andvolatile content of 0.08%.

(Pelletization)

To 100 parts of the resulting saturated polymer was added 0.2 part of1,3,5-trimethyl-2,4,6-tris(3,5-tertbutyl-4-hydroxybenzyl)benzene(Irganox 1330 manufactured by Ciba-Geigy Corp., vapor pressure 1.3×10⁻¹²Pa) as an antioxidant and this was mixed by Henschel mixer andpelletized by a extruder at 230° C.

(Forming)

The pellets were molten and extrusion formed from T-die using a 30 mmφextruder manufactured by Thermoplastic Co. with elevating resintemperature to 280° C. to make a film of 20 cm in width and 100 μm inthickness. In this case, take-up roll temperature of the first step was130° C. and that of the second step was 121° C.

According to visual evaluation, there were neither streaks on thesurface nor internal blowing and thus a transparent film free fromdefects was obtained. Tensile strength of the film was 900 kg/cm². Thisfilm was put between two polarizing sheets whose polarization axes werecrossed at a right angle and was observed under rotation to recognize nobright portion. That is, there was no birefringence. Furthermore, thisfilm was heated at 110° C. for 48 hours in an air oven to find nocoloration.

COMPARATIVE EXAMPLE 1

A reaction mixture obtained by ring opening polymerization andhydrogenation in the same manner as in Example 1 was coagulated onlyonce and vacuum dried at 90° C. for 48 hours to obtain 25.3 parts of ahydrogenation product. Yield was 84%.

The resulting polymer had molecular weights Mn: 6.8×10⁴ and Mw:17.3×10⁴, and Mw/Mn: 2.6, a Tg of 138° C., and a volatile content of0.48%.

In the same manner as in Example 1, antioxidant was added and thepolymer was pelletized and film was prepared therefrom.

The resulting film was visually observed to find that streaks in theform of stripes were formed in the extrusion direction and a largenumber of bubbles were generated in the inner portion and thus the filmhad haze. Tensile strength was 200 kg/cm² which was markedly lower thanthat of the film obtained in Example 1.

EXAMPLE 2

In a 50 liter reaction vessel were charged 200 parts of dehydratedtoluene, 25 parts of tetracyclododecene, 5 parts of dicyclopentadieneand 0.05 part of 1-hexane as monomers in nitrogen atmosphere.

While keeping the temperature at 20° C., 0.5 part of triethylaluminum,1.4 part of triethylamine and 0.17 part of titanium tetrachloride wereadded to the reaction system to carry out polymerization. Temperature ofthe reaction system increased up to 52° C. in 2 minutes after additionof catalyst due to exothermic heat of polymerization reaction.Thereafter, temperature of the reaction system gradually decreased.After the reaction was allowed to proceed for 1 hour, an isopropylalcohol/aqueous ammonia (0.5 part/0.5 part) mixed solution was added tostop the reaction.

The reaction product was poured into 1000 parts of isopropyl alcohol andcoagulated. This coagulated product was dried in the same manner as inExample 1 to obtain 10.5 parts of a ring opening polymer.

The resulting ring opening polymer was dissolved in 200 parts ofcyclohexane and 0.3 part of palladium/carbon catalyst was added andhydrogenation was carried out under the same conditions as in Example 1.After the hydrogenation catalyst was removed by filtration, the productwas coagulated thrice with isopropyl alcohol in the same manner as inExample 1 to obtain 9.5 parts of a hydrogenation product. Hydrogenationrate was at least 99%. Yield was 32%.

The resulting saturated polymer had molecular weights Mn: 30.6×10⁴ andMw: 122×10⁴, and Mw/Mn: 4.0, a Tg of 132° C. and a volatile content of0.05%.

In the same manner as in Example 1, antioxidant was added and thepolymer was extrusion formed into a rod from a die of 3 mmφ.

The resulting rod-like molded article was visually observed to findneither streaks on the surface nor blowing in the inner portion, andthus a transparent rod-like article free from defects was obtained.Tensile strength of the rod was 1200 kg/cm².

This rod-like article was put between two polarizing sheets whosepolarizing axes crossed at a right angle and observed under rotating tofind no birefringence. This rod-like article was heated at 110° C. for48 hours to cause no coloration.

COMPARATIVE EXAMPLE 2

In a 200 liter reaction vessel were charged 70 parts of dehydratedtoluene, 0.5 part of triethylaluminum, 1.4 part of triethylamine, and0.15 part of 1-hexane in nitrogen atmosphere.

While keeping the temperature at 20° C., 22 parts ofmethyltetracyclododecene (MTD), 8 parts of norbornene and 0.17 part oftitanium tetrachloride were continuously added to the reaction systemover a period of 3 hour to carry out polymerization reaction. Thereaction was. allowed to proceed for 1 hour after addition of totalamount of MDT and titanium tetrachloride. Isopropyl alcohol/aqueousammonia (0.5 part/0.5 part) mixed solution was added to stop thereaction and the reaction product was poured into 500 parts of isopropylalcohol to coagulate it. The coagulated polymer was vacuum dried at 60°C. for 10 hours to obtain 25.8 parts of a ring opening polymer as a drypolymer.

The resulting ring opening polymer was hydrogenated in the same manneras in Example 1 and reaction mixture was coagulated only once withisopropyl alcohol and was vacuum dried at 90° C. for 48 hours to obtain22.3 parts of hydrogenation product. Yield was 74%.

The product had molecular weights Mn: 2.9×10⁴, Mw: 4.9×10⁴, and Mw/Mn:2.1, and a Tg of 132° C. and a volatile content of 0.39%.

In the same manner as in Example 1, antioxidant was added to theproduct, this was pelletized and a film was prepared.

The resulting film was visually observed to find that the film wasgreatly waved and was not flat. It is considered that this is due tosmall molecular weight distribution of polymer. Furthermore, streakswere formed in extrusion direction on the surface and internal blowingoccurred and the film was hazed. Such streaks, blowing, haze, andreduction of strength are considered to have been caused by highvolatile content.

EXAMPLE 3

10 parts of the hydrogenation product obtained in Comparative Example 1and 10 parts of the hydrogenation product obtained in Example 2 weredissolved in cyclohexane and blended. This solution was added dropwiseto isopropyl alcohol and coagulated product was vacuum dried to obtain18.6 parts of a blend of resins.

This had molecular weights Mn: 18.7×10⁴, Mw: 97×10⁴, and Mw/Mn: 5.2, andhad a Tg of 132° C. and a volatile content of 0.12%.

In the same manner as in Example 1, antioxidant was added, the productwas pelletized and film was prepared therefrom.

The resulting film was visually observed to find neither streaks on thesurface nor internal blowing, and thus the film was transparent and freefrom defects. Tensile strength was 1050 kg/cm². This film was putbetween two polarizing sheets whose polarizing axes crossed at a rightangle and observed under rotating to find no birefringence. The film washeated at 110° C. for 48 hours to cause no coloration.

Furthermore, a film was formed by reducing the take-up roll temperatureof the first step to 95° C. and that of the second step to 87° C. Theresulting film also had flat surface and had no residual stress.

EXAMPLE 4

Addition copolymerization reaction of ethylene and2-methyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene(M-DMON) was continuously carried out using a 200 liter polymerizerprovided with agitating blade.

That is, from the top of the polymerizer, a solution of M-DMON intoluene a solution of VO(OC₂ H₅)Cl in toluene, and a solution ofethylaluminum sesquichloride [Al(C₂ H₅)₁.5 Cl₁.5 ] in toluene werecontinuously fed to the polymerizer from the top thereof at a rate of 90l/hr, at a rate of 70 l/hr, and at a rate of 40 l/hr so that M-DMONconcentration in the polymerizer was 100 g/l, so that vanadiumconcentration in the polymerizer was 0.3 mmol/l, and so that aluminumconcentration in the polymerizer was 2 mmol/l, respectively.

On the other hand, polymeric liquid was continuously drawn from bottomof the polymerizer so that amount of the polymeric liquid in thepolymerizer was always 100 liters. Further, ethylene was fed at 2300l/hr and nitrogen was fed at 800 l/hr from the top of the polymerizer.

Copolymerization reaction was carried out by controlling temperature to10° C. using a refrigeration medium. A small amount of methanol wasadded to the polymeric liquid drawn from the bottom of the polymerizerto stop polymerization reaction and the liquid was introduced into alarge amount of isopropyl alcohol to precipitate the copolymer produced,which was washed with isopropyl alcohol. The copolymer was obtained at arate of 3 kg/hr. The polymer was vacuum dried at 130° C. for 24 hours.

Loss in weight on heating of the resulting addition copolymer wasmeasured to obtain 0.45%. Since this was unsuitable for the object ofthe present invention, this was again coagulated.

That is, 20 parts of the addition copolymer was dissolved in 100 partsof cyclohexane and the solution was added dropwise to 200 parts ofisopropyl alcohol to coagulate it, followed by vacuum drying at 90° C.for 48 hours to obtain 18.9 parts of addition copolymer.

The copolymer had molecular weights Mn: 7.8×10⁴, Mw: 22×10⁴, and Mw/Mn:2.8, and a Tg of 147° C., and a volatile content of 0.11%.

In the same manner as in Example 1, antioxidant was added to thecopolymer and this was pelletized and a film was prepared therefrom.

The resulting film was visually observed to find neither streaks on thesurface nor internal blowing, and thus the film was transparent and freefrom defects. Tensile strength was 1050 kg/cm². This film was putbetween two polarizing sheets whose polarizing axes crossed at a rightangle and observed under rotating to find no briefringence. The film washeated at 110° C. for 48 hours, resulting in no coloration.

Furthermore, a film was formed by reducing the take-up roll temperatureof the first step to 95° C. and that of the second step to 87° C. Theresulting film also had flat surface and had no residual stress.

EXAMPLE 5

The polymer before addition of antioxidant in Example 1 was pelletizedwithout addition of antioxidant by an extruder at 230° C.

The pellets were extrusion formed from T-die by a 30 mmφ extrudermanufactured by Thermoplastic Co. to obtain a sheet of 20 cm in widthand 1 mm in thickness.

The resulting sheet was visually observed to find neither streaks on thesurface nor internal blowing, and thus the sheet was transparent andfree from defects. Tensile strength was 900 kg/cm². This sheet was putbetween two polarizing sheets whose polarizing axes crossed at a rightangle and observed under rotating to find no birefringence. The sheetwas heated at 110° C. for 48 hours, resulting in slight coloration inyellow.

EXAMPLE 6

To 100 parts of the polymer obtained in Example 1 was added 0.2 part ofpentaerythrityl-tetrakis-3-(3,5-ditert-butyl-4-hydroxyphenyl)propionate(Irganox 1010 manufactured by Ciba-Geigy Corp., vapor pressure 1.3×10⁻¹²Pa) as an antioxidant and this was mixed by Henschel mixer and then, themixture was pelletized and extrusion formed into a sheet in the samemanner as in Example 5.

In the same manner as in Example 5, this sheet was tested to findneither streaks on the surface nor internal blowing. Thus, the sheet wastransparent and free from the defects. Tensile strength was 900 kg/cm²as in Example 5. No birefringence was observed in this sheet. Nocoloration occurred by heating.

EXAMPLE 7

A sheet was obtained in the same manner as in Example 6 except that 0.5part of2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine(Irganox 565 manufactured by Ciba-Geigy Corp., vapor pressure 1.3×10⁻¹²Pa) was used as antioxidant.

Neither streaks on the surface nor internal blowing were seen and thesheet was transparent and free from defects. Tensile strength was 900kg/cm² which was the same as in Example 6. No birefringence was observedin this sheet. No coloration occurred by heating.

EXAMPLE 8

A sheet was obtained in the same manner as in Example 6 except that 2parts of 2,5-di-tert-amylhydroquinone (Nocrack DAH manufactured byOhuchi Shinko Kagaku Co., vapor pressure 1×10⁻⁹ Pa or less) was used asantioxidant.

Neither streaks on the surface nor internal blowing were seen and thesheet was transparent and free from defects. Tensile strength was 900kg/cm² which was the same as in Example 6. No birefringence was observedin this sheet. No coloration occurred by heating.

EXAMPLE 9

A sheet was obtained in the same manner as in Example 6 except that 0.02part of tris(2,4-di-tertbutylphenyl) phosphite (Irganox 168 manufacturedby Ciba-Geigy Corp., vapor pressure 3×10⁻⁸ Pa) was used as antioxidant.

Neither streaks on the surface nor internal blowing were seen and thesheet was transparent and free from defects. Tensile strength was 900kg/cm² which was the same as in Example 6. No birefringence was observedin this sheet. No coloration occurred by heating.

EXAMPLE 10

A sheet was obtained in the same manner as in Example 6 except that 0.2part of 2,2-thio-diethylenebis(3-(3,5-di-tert-butyl-4-hydroxyphenyl))propionate (Irganox 1035 manufactured by Ciba-Geigy Corp., vaporpressure 1.3×10⁻⁹ Pa) was used as antioxidant.

Neither streaks on the surface nor internal blowing were seen and thesheet was transparent and free from defects. Tensile strength was 900kg/cm² which was the same as in Example 6. No birefringence was observedin this sheet. No coloration occurred by heating.

EXAMPLE 11

A sheet was obtained in the same manner as in Example 6 except that 0.1part of Irganox 1010 and 0.1 part of Irganox 168 (vapor pressure1.3×10⁻⁸ Pa) were used as antioxidants.

Neither streaks on the surface nor internal blowing were seen and thesheet was transparent and free from defects. Tensile strength was 900kg/cm² which was the same as in Example 6. No birefringence was observedin this sheet. No coloration occurred by heating.

COMPARATIVE EXAMPLE 3

A sheet was obtained in the same manner as in Example 6 except that 10parts of Irganox 565 (vapor pressure 3×10⁻¹² Pa) was used asantioxidants.

Neither streaks on the surface nor internal blowing were seen and thesheet was transparent and free from defects. Tensile strength was 720kg/cm² which was lower than that in Example 6. When this sheet was putbetween two polarizing sheets and observed to find bright portion anddark portion and thus, birefringence was seen.

EXAMPLE 12

Example of electroconductive composite material is shown below.Materials useful for recording of information, transmission ofinformation and for electronic devices can be provided by processing theelectroconductive composite material by lithography or the like.

The sheet obtained in Example 6 was cut to 10 cm ×10 cm and thereon wasformed an ITO film of 3000 Å thick by RF magnetron sputtering apparatusmanufactured by Nihon Shinku Gijitsu Co. using an alloy target of In₂ O₃/SnO₂ (90:10), thereby to obtain a transparent electroconductive sheethaving a light transmission of 81% for 700 nm and a specific resistanceof 2×10⁻³ Ω.cm.

The resulting electroconductive sheet was observed by a microscope. Thefilm had a flat surface and was free from defects.

EXAMPLE 13

The pellets prepared in Example 1 were dissolved in cyclohexane and acast film of 15 μm thick was formed using the solution on a platinumelectrode and electrolysis polymerization was conducted using a solutionof pyrrole and tetraethylammonium tetrafluoroborate in acetonitrile aselectrolyte solution to obtain a flat transparent electroconductive filmfree from defects and having a light transmittance of 63% and specificresistance of 39 Ω.cm.

EXAMPLE 14

The pellets prepared in Example 2 were press formed into a square plateof 10 cm×10 cm with a thickness of 1 mm and electrolytic copper foil washeat fusion bonded to both sides of the square plate at 280° C. to makea high frequency circuit substrate.

This substrate had a dielectric constant of 2.2, a dielectric loss of4.4×10⁻⁴ and a peel strength of 1 kg/cm.

EXAMPLE 15

The following experiment was conducted in order to examine the effect ofpredrying.

The pellets obtained in Example 1 were extrusion formed as they wereunder the same conditions as in Example 1 to obtain a sheet-like articleof 500 μm thick. Tensile strength of this sheet was 900 kg/cm².

This article was visually observed to find that it was transparent andhad no conspicuously large defects, but this wa observed by a lightmicroscope of 400x magnification in ten fields and the number ofmicrovoids was counted to find microvoids of about 5 μm in size.Further, this sheet was kept in a thermo-hygrostat box of 80° C. and 90%in relative humidity for 1000 hours and then taken out and visuallyobserved to find that it was wholly hazed and had many small crack-likedefects.

Results of tests on sheets obtained by predrying the pellets obtained inExample 1 under various drying conditions by a warm air dryer and thenforming the predried pellets are shown in Table 1 together with theabove results.

                                      TABLE 1                                     __________________________________________________________________________                                      Appearance by                               Predying                Appearance                                                                              visual observa-                             conditions   Properties after molding                                                                           tion after                                  Experi-                                                                           Tempe-   of sheet   Visual                                                                            Observa-                                                                            high tempe-                                 mental                                                                            rature                                                                             Time                                                                              Thickness                                                                           Strength                                                                           obser-                                                                            tion by                                                                             ture and high                               No. (°C.)                                                                       (hrs.)                                                                            (μm)                                                                             (kg/cm.sup.2)                                                                      vation                                                                            microscope                                                                          humidity test                               __________________________________________________________________________    1   No       500   900  Good                                                                              D     Haze                                        2   110  0.5 500   900  "   D     Haze                                        3   110  6.0 500   900  "   A     Good                                        4   120  0.5 500   900  "   B     Somewhat                                                                      haze                                        5   120  2.0 500   900  "   A     Good                                        6   120  4.0 500   900  "   A     "                                           7   130  1.5 500   900  "   A     "                                           __________________________________________________________________________     (Note) Criteria for evaluation of results obtained by observation by          microscope are as follows.                                                    A: No microvoids were observed.                                               B: Two or less microvoids were observed.                                      C: Four or less microvoids were observed.                                     D: At least five microvoids were observed.                               

As is clear from the above Examples, the present invention provides amolding of forming material excellent in heat resistance and waterresistance which comprises a thermoplastic saturated norbornene polymer.Especially, when extrusion formed, the material of the present inventionprovides articles excellent in strength and free from the defects causedby blowing and the like. Furthermore, articles free from microvoids canbe obtained by carrying out predrying treatment. Furthermore, thematerial of the present invention is suitable for optical uses becauseof its excellent optical characteristics such as transparency andbesides, it is suitable as electroconductive composite materials.Moreover, optical recording media can be produced excellent in enduranceand others by using transparent substrates obtained from the material ofthe present invention.

What is claimed is:
 1. A thermoplastic composition comprising athermoplastic saturated norbornene polymer having a number-averagemolecular weight (Mn) of 50,000 to 500,000 and a weight-averagemolecular weight (Mw) of 100,000 to 2,000,000 which are measured by highperformance liquid chromatography, and a molecular weight distribution(Mw/Mn) of at least 2.2, and a maximum volatile content of 0.3% byweight, which contains an antioxidant having a maximum vapor pressure of10⁻⁶ Pa at 20° C. in an amount of 0.01-5 parts by weight based on 100parts by weight of the thermoplastic saturated norbornene polymer.
 2. Athermoplastic composition according to claim 1, wherein thethermoplastic saturated norbornene polymer has a glass transitiontemperature (Tg) of at least 100° C.
 3. A thermoplastic compositionaccording to claim 1, wherein the thermoplastic saturated norbornenepolymer has a hydrogenation rate of at least 90%.
 4. A thermoplasticcomposition according to claim 1, a maximum volatile content in thepolymer is 0.2% by weight.
 5. A thermoplastic composition according toclaim 1, wherein the hydrogenation rate of the polymer is 95% or higherand a maximum volatile content in the polymer is 0.1% by weight.
 6. Athermoplastic composition according to claim 2, wherein Tg of thepolymer is 120°-200° C.
 7. A thermoplastic composition according toclaim 1, the thermoplastic saturated norbornene polymer is a polymer ofnorbornene monomer mainly composed of a tetracyclic norbornene monomer.8. A thermoplastic composition according to claim 7, wherein thenorbornene monomer is a lower alkyl or lower alkylidene groupsubstituted monomer.
 9. A thermoplastic composition according to claim8, wherein the lower alkyl or lower alkylidene substituent has two orthree carbon atoms.
 10. A thermoplastic composition according to claim1, wherein the vapor pressure of the antioxidant is at least 10⁻⁸.
 11. Athermoplastic composition according to claim 1, wherein the antioxidantis a hindered phenol, an aminophenol, a hydroquinone, or a phosphite.12. A thermoplastic composition for films or sheets which is obtained bypelletizing the composition of claim 1 by melt extrusion, and drying theobtained pellets at a maximum temperature of 5° C. below the Tg of saidcopolymer.
 13. A thermoplastic composition for films or sheets accordingto claim 12, wherein the drying is carried out by keeping the pellets ata temperature lower by 5°-30° C. than glass transition temperature (Tg)of the thermoplastic saturated norbornene polymer for at least 1 hour.14. A film or sheet article having a tensile strength of at least 800kg/cm² and substantially free from microvoids which is obtained bymolding the thermoplastic composition according to claim
 1. 15. A filmor sheet article according to claim 14, which is obtained by meltextrusion molding.
 16. An optical material obtained by molding thecomposition of any of claims 1-13.
 17. An electroconductive compositematerial which comprises the film or sheet article of claim 14, on thesurface of which an electroconductive film is formed.
 18. An opticalrecording medium which comprises a transparent substrate comprising thefilm or sheet article of claim 14 or 15 on which a recording thin filmcapable of performing optical recording and/or reading is formed.